Protein extraction from canola oil seed meal

ABSTRACT

The recovery of protein from canola oil seed meal and other oil seed meals in the preparation of canola or other oil seed protein isolate is improved in comparison to conventional toasted meal by the use of a meal which has been air-desolventized at a temperature below about 50° C.

REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119(e) from U.S.Provisional Patent Applications Nos. 60/390,126 filed Jun. 21, 2002 and60/401,782 filed Aug. 8, 2002.

FIELD OF INVENTION

The present invention is concerned with the recovery of protein from oilseed proteins, particularly canola oil seed protein.

BACKGROUND OF THE INVENTION

Canola oil seed is extensively processed for the recovery of canola oiltherefrom. The canola oil seed is crushed to remove most of the oil andthe residual meal is hot solvent extracted, generally using hexane, torecover the remainder of the oil. The residual meal from the solventextraction contains residual hexane and is commonly known as “whiteflake” or less commonly as “marc” meal. The solvent is recovered fromthe meal for reuse before the oil seed meal is disposed of by thecrusher. In the solvent recovery process, the oil seed meal often isheated to a higher temperature of about 120° to 140° C. in a proceduretermed “toasting”. The resulting meal is referred to as “toasted meal”or “high temperature produced meal”.

The residual oil seed meal disposed of by the crusher containssignificant quantities of protein and often is employed as animal feed.There have been prior procedures to recover the canola protein from theresidual canola oil seed meal in the form of a canola protein isolate.

In U.S. Pat. Nos. 5,844,086 and 6,005,076 (“Murray II”), assigned to theassignee hereof and the disclosures of which are incorporated herein byreference, there is described a process for the isolation of proteinisolates from oil seed meal having a significant fat content, includingcanola oil seed meal having such content. The steps involved in thisprocess include solubilizing proteinaceous material from oil seed meal,which also solubilizes fat in the meal and removing fat from theresulting aqueous protein solution. The aqueous protein solution may beseparated from the residual oil seed meal before or after the fatremoval step. The defatted protein solution then is concentrated toincrease the protein concentration while maintaining the ionic strengthsubstantially constant, after which the concentrated protein solutionmay be subjected to a further fat removal step. The concentrated proteinsolution then is diluted to cause the formation of a cloud-like mass ofhighly aggregated protein molecules as discrete protein droplets inmicellar form. The protein micelles are allowed to settle to form anaggregated, coalesced, dense, amorphous, sticky gluten-like proteinisolate mass, termed “protein micellar mass” or PMM, which is separatedfrom the residual aqueous phase and dried.

The protein isolate has a protein content (as determined by Kjeldahl orequivalent method N×6.25) of at least about 90 wt %, is substantiallyundenatured (as determined by differential scanning calorimetry) and hasa low residual fat content. The term “protein content” as used hereinrefers to the quantity of protein in the protein isolate expressed on adry weight basis. The yield of protein isolate obtained using thisprocedure, in terms of the proportion of protein extracted from the oilseed meal which is recovered as dried protein isolate was generally lessthan 40 wt %, typically around 20 wt %.

The procedure described in the aforementioned patents was developed as amodification to and improvement on the procedure for forming a proteinisolate from a variety of protein source materials, including oil seeds,as described in U.S. Pat. No. 4,208,323 (Murray IB), the disclosure ofwhich is incorporated herein by reference. The oil seed meals availablein 1980, when U.S. Pat. No. 4,208,323 issued, did not have the fatcontamination levels of canola oil seed meals at the time of Murray IIpatents, and, as a consequence, the procedure of U.S. Pat. No. 4,208,323cannot produce from such oil seed meals processed according to theMurray II process, proteinaceous materials which have more than 90 wt %protein content. There is no description of any specific experiments inU.S. Pat. No. 4,208,323 carried out using rapeseed (canola) meal as thestarting material.

U.S. Pat. No. 4,208,323 itself was designed to be an improvement on theprocess described in U.S. Pat. Nos. 4,169,090 and 4,285,862 (Murray IA),incorporated herein by reference, by the introduction of theconcentration step prior to dilution to form the PMM. The latter stepserved to improve the yield of protein isolate from around 20% for theMurray IA process.

In copending U.S. Patent Applications Nos. 60/288,415 filed May 4, 2001,60/326,987 filed Oct. 5, 2001, 60/331,066 filed Nov. 7, 2001, 60/333,494filed Nov. 26, 2001, 60/374,801 filed Apr. 24, 2002 and U.S. patentapplication Ser. No. 10/137,391 filed May 3, 2002 (WO 02/089597), allassigned to the assignee hereof and the disclosures of which areincorporated herein by reference, there is described a process forproducing a protein isolate of high purity, containing at least about100 wt % protein (N×6.25). In the aforementioned US Patent Applications,the protein isolate is made by a process in which oil seed meal isextracted with a food grade salt solution, the resulting proteinsolution, after an initial treatment with a colourant adsorbent, ifdesired, is concentrated to a protein content of at least about 200 g/L,and the concentrated protein solution is diluted in chilled water toform protein micelles, which are allowed to settle to form anaggregated, coalesced, dense amorphous, sticky gluten-like proteinisolate mass, termed “protein micellar mass” or PMM, which is separatedfrom residual aqueous phase and may be used as such or dried.

In one embodiment of the process described above and as specificallydescribed in U.S. Patent Applications Nos. 60/326,987, 60/331,066,60/333,494, 60/374,801 and Ser. No. 10/137,391, the supernatant from thePMM settling step is processed to recover a protein isolate comprisingdried protein from wet PMM and supernatant. This procedure may beeffected by initially concentrating the supernatant usingultrafiltration membranes, mixing the concentrated supernatant with thewet PMM and drying the mixture. The resulting canola protein isolate hasa high purity of at least about 90 wt %, preferably at least about 100wt %, protein (N×6.25).

In another embodiment of the process described above and assignificantly specifically described in Applications Nos. 60/331,066,60/333,494, 60/374,801 and Ser. No. 10/137,391, the supernatant from thePMM settling step is processed to recover a protein from thesupernatant. This procedure may be effected by initially concentratingthe supernatant using ultrafiltration membranes and drying theconcentrate. The resulting canola protein isolate has a high purity ofat least about 90 wt %, preferably at least about 100 wt %, protein(N×6.25).

The procedures described in the aforementioned US Patent Applicationsare essentially batch procedures. In copending U.S. Patent ApplicationsNos. 60/331,646 filed Nov. 20, 2001, 60/383,809 filed May 30, 2002 and10/298,678 filed Nov. 19, 2002, assigned to the assignee hereof and thedisclosures of which are incorporated herein by reference, there isdescribed a continuous process for making canola protein isolates. Inaccordance therewith, canola oil seed meal is continuously mixed with asalt solution, the mixture is conveyed through a pipe while extractingprotein from the canola oil seed meal to form an aqueous proteinsolution, the aqueous protein solution is continuously separated fromresidual canola oil seed meal, the aqueous protein solution iscontinuously conveyed through a selective membrane operation to increasethe protein content of the aqueous protein solution to at least about200 g/L while maintaining the ionic strength substantially constant, theresulting concentrated protein solution is continuously mixed withchilled water to cause the formation of protein micelles, and theprotein micelles are continuously permitted to settle while thesupernatant is continuously overflowed until the desired amount of PMMhas accumulated in the settling vessel. The PMM is removed from thesettling vessel and may be dried. The PMM has a protein content of atleast about 90 wt % (N×6.25), preferably at least about 100 wt %.

The experimentation described in such prior U.S. patent applications iscarried out on commercially-available oil seed meal which has beendesolventized in a conventional desolventizer-toasting operation. Usingsuch materials as the oil seed meal for production of oil seed proteinisolate, results in extraction of less than about 30 wt % of the proteinpresent in the oil seed, possibly due to denaturation of protein by thehigh temperature desolventizing operation.

SUMMARY OF THE INVENTION

It has now surprisingly been found that the amount of protein which canbe extracted from canola oil seed protein meal can be significantlyincreased if the extraction is effected on ambient temperaturedesolventized meal. The ability to extract more protein from the mealimproves the overall economics of the process. In addition a product ofimproved quality is obtained.

In accordance with one aspect of the present invention, there isprovided a process of preparing a protein isolate, which comprises (a)crushing oil seeds to form oil and oil seed meal therefrom, (b) solventextracting the oil seed meal to recover residual oil therefrom, (c)removing solvent from the extracted oil seed meal at a temperature ofbelow about 50° C. to provide a desolventized oil seed meal, (d)extracting the desolventized oil seed meal to cause solubilization ofprotein in the desolventized oil seed meal and to form an aqueousprotein solution having a pH of about 5 to about 6.8, (e) separating theaqueous protein solution from residual oil seed meal, (f) increasing theprotein concentration of the aqueous protein solution while maintainingthe ionic strength substantially constant by using a selective membranetechnique to provide a concentrated protein solution, (g) diluting theconcentrated protein solution into chilled water having a temperature ofbelow about 15° C. to cause the formation of discrete protein particlesin the aqueous phase at least partially in the form of micelles, (h)settling the protein micelles to form an amorphous, sticky, gelatinous,gluten-like protein micellar mass, and (i) recovering the proteinmicellar mass from supernatant, the protein micellar mass having aprotein content of at least about 90 wt % (N×6.25) on a dry weightbasis.

The present invention uses white flake or marc meal which has beendesolventized at moderate temperatures below about 50° C., preferably atabout 15° to about 30° C. Desolventizing may be effected by air dryingthe meal or by vacuum stripping.

The protein may be extracted and recovered from the ambient temperaturedesolventized meal by either a batch process, a semi-batch process or acontinuous process as generally described in the aforementioned U.S.patent applications.

The protein isolate produced according to the process herein may be usedin conventional applications of protein isolates, such as, proteinfortification of processed foods, emulsification of oils, body formersin baked goods and foaming agents in products which entrap gases. Inaddition, the protein isolate may be formed into protein fibers, usefulin meat analogs, may be used as an egg white substitute or extender infood products where egg white is used as a binder. The canola proteinisolate may be used as nutritional supplements. Other uses of the canolaprotein isolate are in pet foods, animal feed and in industrial andcosmetic applications and in personal care products.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 to 3 are HPLC chromatograms of extractions of canola oil seedmeal which has been air-desolventized meal at room temperature using0.05 M NaCl (FIG. 1) and 0.10 M NaCl (FIG. 2) and at 60° C. in theabsence of salt (FIG. 3).

GENERAL DESCRIPTION OF INVENTION

The process of the invention commences with oil seed, particularlycanola oil seed, although the process may be applied to other oil seeds,such as soybean, traditional rapeseed, traditional flax, linola,sunflower and mustard oil seed meals. The invention is more particularlydescribed herein with respect to canola oil seed meal.

The oil seed is washed to recover oil therefrom. Following separation ofthe oil, the residual meal is solvent extracted, usually using hexane,to recover residual amounts of oil from the meal. The resulting mealthen is desolventized in accordance with the present invention at atemperature below about 50° C., preferably at about 15° to about 30° C.By effecting desolventizing in this manner, it has been found that theamount of protein which can be extracted from the meal is significantlyincreased.

The oil seed meal which is processed in this manner may be processed asdescribed in the Murray I or II patents to recover protein isolate fromthe oil seed meal, details of which are described therein. Preferably,the procedure described in the aforementioned copending U.S. PatentApplications Nos. 60/288,415, 60/326,987, 60/331,066, 60/333,494,60/372,165, 60/374,801 and Ser. No. 10/137,391 (WO 02/089567) isemployed since there are obtained thereby improved yields of driedprotein isolate, in terms of the proportion of the protein extractedfrom the oil seed meal which is recovered as protein isolate and aprotein isolate of high protein content is obtained, usually at leastabout 100 wt % as determined by the Kjeldahl method as percent nitrogen(N) and multiplied by a factor of 6.25. Alternatively, the continuousprocess described in the aforementioned U.S. Applications Nos.60/331,646, 60/383,809 and Ser. No. 10/298,678 may be employed. Detailsof these preferred procedures as applied to canola protein isolate aredescribed below.

It will be understood that the processing of the oil seed to recover oiltherefrom may be effected in a different facility from that at which theprotein isolate is recovered from the oil seed meal. Alternatively, theoperations may be combined at a single facility.

The initial step of the process of separating the canola protein isolateinvolves solubilizing proteinaceous material from canola oil seed meal.The proteinaceous material recovered from canola seed meal may be theprotein naturally occurring in canola seed or other oil seed or theproteinaceous material may be a protein modified by genetic manipulationbut possessing characteristic hydrophobic and polar properties of thenatural protein. Canola oil seed is also known as rapeseed or oil seedrape.

Protein solubilization is effected most efficiently by using a foodgrade salt solution since the presence of the salt enhances the removalof soluble protein from the oil seed meal. Where the canola proteinisolate is intended for non-food uses, non-food grade chemicals may beemployed. The food grade salt usually is sodium chloride, although othersalts, such as, potassium chloride, may be used. The food grade saltsolution has an ionic strength of at least about 0.10, preferably atleast about 0.15, to enable solubilization of significant quantities ofprotein to be effected. As the ionic strength of the salt solutionincreases, the degree of solubilization of protein in the oil seed mealinitially increases until a maximum value is achieved. Any subsequentincrease in ionic strength does not increase the total proteinsolubilized. The ionic strength of the food grade salt solution whichcauses maximum protein solubilization varies depending on the saltconcerned and the oil seed meal chosen.

In view of the greater degree of dilution required for proteinprecipitation with increasing ionic strengths, it is usually preferredto utilize an ionic strength value less than about 0.8, and morepreferably a value of about 0.15 to about 0.6.

In a batch process, the salt solubilization of the protein is effectedat a temperature of at least about 5° and preferably up to about 35° C.,preferably accompanied by agitation to decrease the solubilization time,which is usually about 10 to about 60 minutes. It is preferred to effectthe solubilization to extract substantially the maximum amount ofprotein from the oil seed meal, so as to provide an overall high productyield.

The lower temperature limit of about 5° C. is chosen sincesolubilization is impractically slow below this temperature while theupper preferred temperature limit of about 35° C. is chosen since theprocess becomes uneconomic at higher temperature levels in a batch mode.

In a continuous process, the extraction of the protein from the canolaoil seed meal is carried out in any manner consistent with effecting acontinuous extraction of protein from the canola oil seed meal. In oneembodiment, the canola oil seed meal is continuously mixed with a saltsolution and the mixture is conveyed through a pipe or conduit having alength and at a flow rate for a residence time sufficient to effect thedesired extraction in accordance with the parameters described herein.In such continuous procedure, the salt solubilization step is effectedrapidly, in a time of up to about 10 minutes, preferably to effectsolubilization to extract substantially the maximum amount of proteinfrom the canola oil seed meal. The solubilization in the continuousprocedure preferably is effected at elevated temperatures, preferablyabove about 35° C., generally up to about 65° C. or more.

The aqueous food grade salt solution and the canola oil seed meal have anatural pH of about 5 to about 6.8 to enable a protein isolate to beformed by the micellar route, as described in more detail below.

At and close to the limits of the pH range, protein isolate formationoccurs only partly through the micelle route and in lower yields thanattainable elsewhere in the pH range. For these reasons, pH values ofabout 5.3 to about 6.2 are preferred.

The pH of the food grade salt solution may be adjusted to any desiredvalue within the range of about 5 to about 6.8 for use in the extractionstep by the use of any convenient food grade acid, usually hydrochloricacid, or food grade alkali, usually sodium hydroxide, as required. Wherethe canola protein isolate is intended for non-food uses, then non-foodgrade chemicals may be used.

The concentration of oil seed meal in the food grade salt solutionduring the solubilization step may vary widely. Typical concentrationvalues are about 5 to about 15% w/v.

The protein extraction step with the aqueous salt solution has theadditional effect of solubilizing fats which may be present in thecanola meal, which then results in the fats being present in the aqueousphase.

The protein solution resulting from the extraction step generally has aprotein concentration of about 5 to about 40 g/L, preferably about 10 toabout 30 g/L.

The aqueous phase resulting from the extraction step then may beseparated from the residual canola meal, in any convenient manner, suchas by employing vacuum filtration, followed by centrifugation and/orfiltration to remove residual meal. The separated residual meal may bedried for disposal.

The colour of the final canola protein isolate can be improved to obtaina lighter and less intense yellow colour by the mixing of powderedactivated carbon or other pigment adsorbing agent with the separatedaqueous protein solution and subsequently removing the adsorbent,conveniently by filtration, to provide a protein solution. Diafiltrationof the separated aqueous protein solution, before or afterconcentration, as described below, also may be used for pigment removal.

Such pigment removal step may be carried out under any convenientconditions, generally at the ambient temperature of the separatedaqueous protein solution, employing any suitable pigment adsorbingagent. For powdered activated carbon, an amount of about 0.025% to about5% w/v, preferably about 0.05% to about 2% w/v, is employed.

Where the canola seed meal contains significant quantities of fat, asdescribed in the aforementioned U.S. Pat. Nos. 5,844,086 and 6,005,076,then the defatting steps described therein may be effected on theseparated aqueous protein solution and on the concentrated aqueousprotein solution discussed below. When the colour improvement step iscarried out, such step may be effected after the first defatting step.

As an alternative to extracting the oil seed meal with an aqueous foodgrade salt solution, such extraction may be made using water alone,although the utilization of water alone tends to extract less proteinfrom the oil seed meal than the aqueous food grade salt solution. Wheresuch alternative is employed, then the food grade salt, in theconcentrations discussed above, may be added to the protein solutionafter separation from the residual oil seed meal in order to maintainthe protein in solution during the concentration step described below.When a colour removal step and/or a first fat removal step is carriedout, the food grade salt generally is added after completion of suchoperations.

Another alternative procedure is to extract the oil seed meal with thefood grade salt solution at a relatively high pH value above about 6.8,generally up to about 9.8. The pH of the food grade salt solution, maybe adjusted in pH to the alkaline value by the use of any convenientfood-grade alkali, such as aqueous sodium hydroxide solution. Where suchalternative is employed, the aqueous phase resulting from the oil seedmeal extraction step then is separated from the residual canola meal, inany convenient manner, such as by employing vacuum filtration, followedby centrifugation and/or filtration to remove residual meal. Theseparated residual meal may be dried for disposal.

The aqueous protein solution resulting from the high pH extraction stepthen is pH adjusted to the range of about 5 to about 6.8, preferablyabout 5.3 to about 6.2, as discussed above, prior to further processingas discussed below. Such pH adjustment may be effected using anyconvenient food grade acid, such as hydrochloric acid.

The aqueous protein solution then is concentrated to increase theprotein concentration thereof while maintaining the ionic strengththereof substantially constant. Such concentration generally is effectedto provide a concentrated protein solution having a proteinconcentration of at least about 200 g/L, preferably at least about 250g/L.

The concentration step may be effected in any convenient mannerconsistent with batch or continuous operation, such as by employing anyconvenient selective membrane technique, such as ultrafiltration ordiafiltration, using membranes, such as hollow-fibre membranes orspiral-wound membranes, with a suitable molecular weight cut-off, suchas about 3000 to about 50,000 daltons, having regard to differingmembrane materials and configurations, and, for continuous operation,dimensioned to permit the desired degree of concentration as the aqueousprotein solution passes through the membranes.

The concentration step may be effected at any convenient temperature,generally about 20° to about 60° C., and for the period of time toeffect the desired degree of concentration. The temperature and otherconditions used to some degree depend upon the membrane equipment usedto effect the concentration and the desired protein concentration of thesolution.

The concentrating of the protein solution to a concentration above about200 g/L in this step not only increases the process yield to levelsabove about 40% in terms of the proportion of extracted protein which isrecovered as dried protein isolate, preferably above about 80%, but alsodecreases the salt concentration of the final protein isolate afterdrying. The ability to control the salt concentration of the isolate isimportant in applications of the isolate where variations in saltconcentrations affect the functional and sensory properties in aspecific food application

As is well known, ultrafiltration and similar selective membranetechniques permit low molecular weight species to pass therethroughwhile preventing higher molecular weight species from so doing. The lowmolecular weight species include not only the ionic species of the foodgrade salt but also low molecular weight materials extracted from thesource material, such as, carbohydrates, pigments and anti-nutritionalfactors, as well as any low molecular weight forms of the protein. Themolecular weight cut-off of the membrane is usually chosen to ensureretention of a significant proportion of the protein in the solution,while permitting contaminants to pass through having regard to thedifferent membrane materials and configurations.

Depending on the temperature employed in the concentration step, theconcentrated protein solution may be warmed to a temperature of at leastabout 200, and up to about 60° C., preferably about 25° to about 40° C.,to decrease the viscosity of the concentrated protein solution tofacilitate performance of the subsequent dilution step and micelleformation. The concentrated protein solution should not be heated beyonda temperature above which the temperature of the concentrated proteinsolution does not permit micelle formation on dilution by chilled water.The concentrated protein solution may be subject to a farther defattingoperation, if required, as described in the aforementioned U.S. Pat.Nos. 5,844,086 and 6,005,076.

The concentrated protein solution resulting from the concentration stepand optional defatting step then is diluted to effect micelle formationby mixing the concentrated protein solution with chilled water havingthe volume required to achieve the degree of dilution desired. Dependingon the proportion of canola protein desired to be obtained by themicelle route and the proportion from the supernatant, the degree ofdilution of the concentrated protein solution may be varied. With higherdilution levels, in general, a greater proportion of the canola proteinremains in the aqueous phase.

When it is desired to provide the greatest proportion of the protein bythe micelle route, the concentrated protein solution is diluted by about15 fold or less, preferably about 10 fold or less.

The chilled water with which the concentrated protein solution is mixedhas a temperature of less than about 15° C., generally about 3° to about15° C., preferably less than about 10° C., since improved yields ofprotein isolate in the form of protein micellar mass are attained withthese colder temperatures at the dilution factors used.

In a batch operation, the batch of concentrated protein solution isadded to a static body of chilled water having the desired volume, asdiscussed above. The dilution of the concentrated protein solution andconsequential decrease in ionic strength causes the formation of acloud-like mass of highly associated protein molecules in the form ofdiscrete protein droplets in micellar form. In the batch procedure, theprotein micelles are allowed to settle in the body of chilled water toform an aggregated, coalesced, dense, amorphous sticky gluten-likeprotein micellar mass PMM. The settling may be assisted, such as bycentrifugation. Such induced settling decreases the liquid content ofthe protein micellar mass, thereby decreasing the moisture contentgenerally from about 70% by weight to about 95% by weight to a value ofgenerally about 50% by weight to about 80% by weight of the totalmicellar mass. Decreasing the moisture content of the micellar mass inthis way also decreases the occluded salt content of the micellar mass,and hence the salt content of dried isolate.

Alternatively, the dilution operation may be carried out continuously bycontinuously passing the concentrated protein solution to one inlet of aT-shaped pipe, while the diluting water is fed to the other inlet of theT-shaped pipe, permitting mixing in the pipe. The diluting water is fedinto the T-shaped pipe at a rate sufficient to achieve the desireddegree of dilution.

The mixing of the concentrated protein solution and the diluting waterin the pipe initiates the formation of protein micelles and the mixtureis continuously fed from the outlet from the T-shaped pipe into asettling vessel, from which, when full, supernatant is permitted tooverflow. The mixture preferably is fed into the body of liquid in thesettling vessel in a manner which minimizes turbulence within the bodyof liquid.

In the continuous procedure, the protein micelles are allowed to settlein the settling vessel to form an aggregated, coalesced, dense,amorphous, sticky, gluten-like protein micellar mass (PMM) and theprocedure is continued until a desired quantity of the PMM hasaccumulated in the bottom of the settling vessel, whereupon theaccumulated PMM is removed from the settling vessel.

The combination of process parameters of concentrating of the proteinsolution to a protein content of at least about 200 g/L and the use of adilution factor less than about 15, result in higher yields, oftensignificantly higher yields, in terms of recovery of protein in the formof protein micellar mass from the original meal extract, and much purerisolates in terms of protein content than achieved using any of theknown prior art protein isolate forming procedures discussed in theaforementioned U.S. patent applications.

The settled isolate is separated from the residual aqueous phase orsupernatant, by such methods as decantation of the residual aqueousphase from the settled mass or centrifugation. The PMM may be used inthe wet form or may be dried, by any convenient technique, such as spraydrying, freeze drying or vacuum drum drying, to a dry form. The dry PMMhas a high protein content, in excess of about 90 wt % protein,preferably at least about 100 wt % protein (calculated as KjeldahlN×6.25), and is substantially undenatured (as determined by differentialscanning calorimetry). The dry PMM isolated from fatty oil seed mealalso has a low residual fat content, when the procedures of theaforementioned U.S. Pat. Nos. 5,844,086 and 6,005,076 are employed,which may be below about 1 wt %.

The supernatant from the PMM formation and settling step containssignificant amounts of canola protein, not precipitated in the dilutionstep, and is processed to recover canola protein isolate therefrom. Thesupernatant from the dilution step, following removal of the PMM, isconcentrated to increase the protein concentration thereof. Suchconcentration is effected using any convenient selective membranetechnique, such as ultrafiltration, using membranes with a suitablemolecular weight cut-off permitting low molecular weight species,including the food grade salt and other non-proteinaceous low molecularweight materials extracted from the protein source material, to passthrough the membrane, while retaining canola protein in the solution.Ultrafiltration membranes having a molecular weight cut-off of about3000 to 10,000 daltons, having regard to differing membrane materialsand configuration, may be used. Concentration of the supernatant in thisway also reduces the volume of liquid required to be dried to recoverthe protein. The supernatant generally is concentrated to a proteinconcentration of about 100 to about 400 g/L, preferably about 200 toabout 300 g/L, prior to drying. Such concentration operation may becarried out in a batch mode or in a continuous operation, as describedabove for the protein solution concentration step.

The concentrated supernatant may be dried by any convenient technique,such as spray drying, freeze drying or vacuum drum-drying, to a dry formto provide a further canola protein isolate. Such further canola proteinisolate has a high protein content, in excess of about 90 wt %,preferably at least about 100 wt % protein (calculated as N×6.25) and issubstantially undenatured (as determined by differential scanningcalorimetry).

If desired, at least a portion of the wet PMM may be combined with atleast a portion of the concentrated supernatant prior to drying thecombined protein streams by any convenient technique to provide acombined canola protein isolate composition according to one invention.The relative proportions of the proteinaceous materials mixed togethermay be chosen to provide a canola protein isolate composition having adesired profile of 2S/7S/12S proteins. Alternatively, the dried proteinisolates may be combined in any desired proportions-to provide anydesired specific 2S/7S/12S protein profile in the mixture. The combinedcanola protein isolate composition has a high protein content, in excessof about 90 wt %, preferably at least about 100 wt %, (calculated asN×6.25) and is substantially undenatured (as determined by differentialscanning calorimetry).

In another alternative procedure, where a portion only of theconcentrated supernatant is mixed with a part only of the PMM and theresulting mixture dried, the remainder of the concentrated supernatantmay be dried as may any of the remainder of the PMM. Further, dried PMMand dried supernatant also may be dry mixed in any desired relativeproportions, as discussed above.

By operating in this manner, a number of canola protein isolates may berecovered, in the form of dried PMM, dried supernatant and driedmixtures of various proportions by weight of PMM and supernatant,generally from about 5:95 to about 95:5 by weight, which may bedesirable for attaining differing functional and nutritional properties.

As an alternative to dilution of the concentrated protein solution intochilled water and processing of the resulting precipitate andsupernatant as described above, protein may be recovered from theconcentrated protein solution by dialyzing the concentrated proteinsolution to reduce the salt content thereof. The reduction of the saltcontent of the concentrated protein solution results in the formation ofprotein micelles in the dialysis tubing. Following dialysis, the proteinmicelles may be permitted to settle, collected and dried, as discussedabove. The supernatant from the protein micelle settling step may beprocessed, as discussed above, to recover further protein therefrom.Alternatively, the contents of the dialysis tubing may be directlydried. The latter alternative procedure is useful where small laboratoryscale quantities of protein are desired.

EXAMPLES Example 1

This Example illustrates the process of the invention.

75 g samples of canola oil seed meal which had been air-desolventized atambient temperature (20° C.) were added to 500 ml samples of 0.15 M NaClsolution at ambient or room temperature (RT), 55° C., 60° C. and 65° C.,agitated for 30 minutes while maintaining the temperature of thesolution substantially constant to provide aqueous protein solutions.Samples of aqueous protein solution were taken at 5, 10, 15, 20 and 30minutes for analysis. The spent meal was separated by centrifugation at10,000×g for 5 minutes and freeze-dried.

The protein concentrations of the various aqueous protein solutionsobtained in these experiments were determined and the results appear inthe following Table I: TABLE I Protein Concentration in Extracts (wt %)Extraction Time (min) RT* 55° C. 60° C. 65° C. 5 2.97 3.33 3.33 3.37 103.21 3.39 3.52 3.40 15 3.22 3.47 3.59 3.41 20 3.21 3.51 3.53 3.39 303.17 3.46 3.63 3.14*Room Temperature (20° C.)

As may be seen from this data, extraction at elevated temperatureproceeded faster than at room temperature. Extraction in terms ofmaximum protein concentration reached equilibrium within 5 minutes atelevated temperatures, while extraction at room temperature usually took10 minutes. As the extraction temperature rose from room temperature to60° C., the protein concentration of the extract increased by over 10%while a further rise in temperature resulted in a slightly decreasedextractability.

Based on the protein concentration data set forth in Table I, proteinextractabilities were calculated and the results appear in the followingTable II: TABLE II Protein Extractability at Different Temperatures*Temperature (° C.) Extractability (wt %) RT 50.1 55 54.0 60 55.9 65 53.9*Defined as percentage of the amount of protein extracted as of thetotal amount of protein in the meal

As may be seen from this data, the extractability of the protein in thecanola oil seed meal exceeded 50 wt % at all temperatures tested, aconsiderable improvement over the maximum 30 wt % achieved withcommercial toasted canola oil seed meal.

Example 2

This Example shows the effects of certain parameters on proteinextractability.

In a first set of experiments, 50 g samples of (a) canola oil seed mealwhich had been air-desolventized at ambient temperature (20° C.) or (b)commercial canola oil seed meal which had been desolventized byconventional toasting (toasted commercial meal) were added to 500 mLsamples of 0.05 M or 0.10 M NaCl solution at room temperature (20° C.)and stirred for 15 minutes. The slurry was centrifuged at 5000×g for 10minutes to remove the spent meal.

In a second set of experiments, 500 mL of water with no salt added wasfirst heated to 60° C. on a hot plate stirrer and then (a) 50 g ofcanola oil seed meal which had been air-desolventized at ambienttemperature (20° C.) Marc meal) or (b) commercial canola oil seed mealwhich had been desolventized by conventional toasting (commercial meal)was added and stirred for 15 minutes while the temperature wasmaintained. The extract was separated from the spent meal bycentrifugation at 5000×g for 10 minutes.

The protein concentration of the various aqueous protein solutionsobtained in these experiments were determined and appear in thefollowing Table V: TABLE V Protein Concentrations in Extracts (wt %)0.05 M saline 0.10 M saline 60° C. water Ambient temperature 2.09 2.041.38 desolventized meal Toasted commercial meal 0.75 0.85 0.60

The protein extractability from the meals was determined from theprotein concentration data of Table V and this data is presented inTable VI: TABLE VI Protein Extractability (wt %)* 0.05 M saline 0.10 Msaline 60° C. water Ambient temperature 49.6 48.4 32.7 desolventizedmeal Toasted commercial meal 17.0 20.0 14.0*Defined as percentage of the amount of protein extracted as of thetotal amount of protein in the meal.

Table VI shows that the protein extractability of the Marc meal at bothsalt concentrations were comparable with a 15 wt % meal and 0.15 M saltconcentration at room temperature (see Table II above). The proteinextraction of the Marc meal at 0.05 M NaCl was comparable with that at0.10 M NaCl. In the case of no salt added, the protein extractabilitywas substantially lower at the elevated temperature than that using 0.05and 0.10 M salt at room temperature. In all cases, however, the proteinextractability and protein concentrations were significantly higher thanobtained with toasted commercial meal.

A third set of experiments was performed at room temperature in the samemanner as the room temperature experiments described above but a saltconcentration of 0.01M, 0.02M, 0.03M, 0.04M and 0.05M. The proteinextractabilities were determined for each extract and the results appearin the following VII: TABLE VII Protein Extractability of Marc Meal atLow Salt Concentration Salt Concentration (M) Protein Extractability (wt%) 0.05 49.6 0.04 43.4 0.03 38.8 0.02 40.3 0.01 38.5

As may be seen from the data presented in Table VII, a substantialdecrease in protein extractability was observed between saltconcentrations, of 0.04M and 0.05M, suggesting that a minimum saltconcentration to obtain a good yield of protein in the extract solutionis 0.05M.

A Varian high pressure liquid chromatography column (HPLC), using a 30cm BioSep S3000 Size Exclusion Chromatography (SEC) column containinghydrophilic-bonded silica rigid support media, 5-micron diameter,290-Angstrom pore size, capable of separating globular proteins from5,000 to 700,000 dalton size, was run with a series of standards ofprotein origin to determine the residence time (RT) of each component,as measured at A280 nm, at an elution flow rate of 1.0 mL/min. TheBioRad standard proteins cover a range from 17,000 daltons (myoglobulin)to 670,000 daltons (thyroglobulin) with Vitamin B12 added as a lowmolecular mass marker at 1,350 daltons. Each component is measured at280 nm at an elution flow rate of 1.0 mL/min. Saline solution, pHadjusted and containing sodium azide as an antibacterial agent, was usedas the column solvent and to dissolve dry samples. Eluant was discardedafter UV detection as only 25 to 50 microliters of sample are requiredper run. The HPLC Prostar system automatically calculated retentiontimes and peak areas and printed out a summary report.

Samples of the extracts prepared as described in this Example were runon each column. The peak area counts were converted to percentage foreach peak. All peaks on different runs were taken into calculation andthen the three major protein fractions, 12S, 7S and 2S, wererecalculated separately. The results obtained are shown in the graphicaldata of FIGS. 1 to 3.

Each chromatogram showed a distinct peak representing 7S canola proteinfraction and a small bump of 12S canola protein fraction. The peak forthe 2S canola protein fraction was present among peaks for othercomponents of the extract. The peaks in the lower molecular weight endof the chromatogram were not properly identified, but likely correspondto non-protein nitrogenous compounds, such as short peptides and freeamino acids, as well as other meal components, such as phenoliccompounds, glucosinolates and phytates.

Example 3

This Example further illustrates the preparation of a canola proteinisolate using air-desolventized canola oil seed meal.

160 kg of marc canola meal which had been air-desolventized at 20° C.was added to 1602 L of 0.15 M NaCl at 17.6° C. and agitated for 30minutes to provide an aqueous protein solution having a protein contentof 21.4 g/L. 0.05 wt % of ascorbic acid was added after 15 minutes ofthe extraction time. The percentage protein in the meal which wasextracted was 51.6%.

The residual canola meal was removed and washed on a vacuum filter belt.The resulting protein solution was clarified by centrifugation andfiltration to produce 1270 L of a clarified protein solution having aprotein content of 16.2 g/L.

1270 L of the protein extract solution was reduced in volume to 71 L byconcentration on an ultrafiltration system using 5000 dalton molecularweight cut-off membranes. The protein extract solution then wasdiafiltered on a diafiltration system using 5000 dalton molecular weightcut-off membranes with 5000 L (5 retentate volumes) of 0.15 M salinesolution containing 0.05 wt % ascorbic acid to a fmal volume of 31 Lwith a protein content of 226 g/L. The retentate was pasteurized at 60°C. for 10 minutes.

The concentrated and diafiltered solution was divided into three batchesof 30 L, 30 L and 8 L respectively. A first batch at 30° C. was diluted1:15 into 450 L of filtered water at 4° C. A white cloud of proteinmicelles formed immediately and was allowed to settle. The upperdiluting water was removed. This procedure was repeated for the secondand third batches. The precipitated, viscous, sticky mass (PMM) wasremoved from the bottom of the vessel. The dried protein was found tohave a protein content of 102.4 wt % (N×6.25) d.b. (Percentage nitrogenvalues were determined using a Leco FP 328 Nitrogen Determinator). Theproduct was given designation BW-AA020-C17-03A-C300.

988 L of supernatant from the protein micelle formation wereconcentrated to 38 L on a ultrafiltration system using 5000 daltonmolecular weight cut-off membranes. The concentrated supernatant thenwas dilafiltered on a diafiltration system using 5000 dalton molecularweight cut-off membranes with 130 L (4 retentate volumes) of water to afinal volume of 38 L with a protein content of 194 g/L.

The concentrated and diafiltered solution was diluted to a pumpableconsistency and was then spray dried. The dried protein was found tohave a protein content of 97.6 wt % (N×6.25) d.b. The product was givendesignation BW-AA020-C17-03A-C200.

SUMMARY OF DISCLOSURE

In summary of this disclosure, the present invention provides animproved process for making oil seed protein isolates from oil seedmeals by using an ambient temperature desolventized meal to provide agreater degree of extraction of protein from the meal leading toeconomic benefits. Modifications are possible within the scope of thisinvention.

1. A process of preparing a protein isolate, which comprises: (a)crushing oil seeds to form oil and oil seed meal therefrom, (b) solventextracting the oil seed meal to recover residual oil therefrom, (c)removing solvent from the extracted oil seed meal at a temperature ofbelow about 50° C. to provide a desolventized oil seed meal, (d)extracting the desolventized oil seed meal to cause solubilization ofprotein in said desolventized oil seed meal and to form an aqueousprotein solution having a pH of about 5 to about 6.8, (e) separating theaqueous protein solution from residual oil seed meal, (f) increasing theprotein concentration of said aqueous protein solution while maintainingthe ionic strength substantially constant by using a selective membranetechnique to provide a concentrated protein solution, (g) diluting saidconcentrated protein solution into chilled water having a temperature ofbelow about 15° C. to cause the formation of discrete protein particlesin the aqueous phase at least partially in the form of micelles, (h)settling the protein micelles to form an amorphous, sticky, gelatinous,gluten-like protein micellar mass, and (i) recovering the proteinmicellar mass from supernatant, the protein micellar mass having aprotein content of at least about 90 wt % (N×6.25) on a dry weightbasis.
 2. The process of claim 1 wherein said steps (d) to (i) areeffected in a batch mode of operation.
 3. The process of claim 1 whereinsaid steps (d) to (i) are effected in a semi-continuous mode ofoperation.
 4. The process of claim 1 wherein said steps (d) to (i) areeffected in a continuous mode of operation.
 5. The process of claim 2wherein said extracting of said oil seed meal is effected using anaqueous salt solution having an ionic strength of at least about 0.10and a pH of about 5 to about 6.8 and said aqueous protein solution has aprotein content of about 5 to about 40 g/L.
 6. The process of claim 5wherein said salt solution has an ionic strength of about 0.15 to about0.6.
 7. The process of claim 5 wherein said salt solution has a pH ofabout 5.3 to about 6.2.
 8. The process of claim 5 wherein saidextracting of said oil seed meal is effected with agitation of saidaqueous salt solution for about 10 to about 30 minutes.
 9. The processof claim 8 wherein the concentration of oil seed meal in said aqueoussalt solution during said extracting step is about 5 to about 15% w/v.10. The process of claim 5 wherein said aqueous protein solutionresulting from the extraction step has a concentration of about 10 toabout 30 g/L.
 11. The process of claim 3 wherein said extraction step iseffected by: (i) continuously mixing an oil seed meal with an aqueoussalt solution having an ionic strength of at least about 0.10 and a pHof about 5 to about 6.8 at a temperature of about 5° to about 65° C.,and (ii) continuously conveying said mixture through a pipe whileextracting protein from the oil seed meal to form an aqueous proteinsolution having a protein content of about 5 to about 40 g/L for aperiod of time up to about 10 minutes.
 12. The process of claim 11wherein said salt solution has an ionic strength of about 0.15 to about0.8.
 13. The process of claim 11 wherein the salt solution has a pH ofabout 5.3 to about 6.2.
 14. The process of claim 11 wherein theconcentration of oil seed meal in said aqueous salt solution in saidmixing step is about 5 to about 15% w/v.
 15. The process of claim 11wherein said temperature is at least about 35° C.
 16. The process ofclaim 11 wherein said aqueous protein solution has a protein content ofabout 10 to about 30 g/L.
 17. The process of claim 1 wherein saidextracting of said oil seed meal is effected using an aqueous saltsolution having an ionic strength of at least about 0.10 and a pH ofabout 3 to about 5 or about 6.8 to about 9.9 and, following saidseparation of the aqueous protein solution from residual oil seed meal,the pH of the aqueous protein solution is adjusted to a pH of about 5 toabout 6.8.
 18. The process of claim 17 wherein said salt solution has aionic strength of about 0.15 to about 0.6.
 19. The process of claim 17wherein the pH of the aqueous protein solution is adjusted to a pH of5.3 to about 6.2.
 20. The process of claim 1 wherein said oil seed mealis canola oil seed meal and, following said separating of the aqueousprotein solution from the residual canola seed meal, the aqueous proteinsolution is subjected to a pigment removal step.
 21. The process ofclaim 20 wherein said pigment removal step is effected by diafiltrationof the aqueous protein solution.
 22. The process of claim 20 whereinsaid pigment removal step is effected by mixing a pigment adsorbingagent with the aqueous protein solution and subsequently removing thepigment adsorbing agent from the aqueous protein solution.
 23. Theprocess of claim 22 wherein the pigment adsorbing agent is powderedactivated carbon.
 24. The process of claim 1 wherein said oil seed mealis extracted with water and subsequent thereto salt is added to theresulting aqueous protein solution to provide an aqueous proteinsolution having an ionic strength of at least about 0.10.
 25. Theprocess of claim 1 wherein said concentration step is effected byultrafiltration to produce a concentrated protein solution having aprotein content of at least about 200 g/L.
 26. The process of claim 25wherein said concentration step is effected to produce a concentratedprotein solution having a protein content of at least about 250 g/L. 27.The process of claim 25 wherein said concentrated protein solution iswarmed to a temperature of at least about 20° C. to decrease theviscosity of the concentrated protein solution but not beyond atemperature above which the temperature of the concentrated proteinsolution does not permit micelle formation.
 28. The process of claim 27wherein said concentrated protein solution is warmed to a temperature ofabout 25° C. to about 40° C.
 29. The process of claim 2 wherein saidconcentrated protein solution is diluted by about 15 fold or less byadding the concentrated protein solution into a body of water having thevolume required to achieve the desired degree of dilution.
 30. Theprocess of claim 29 wherein said body of water has a temperature of lessthan about 10° C.
 31. The process of claim 30 wherein said concentratedprotein solution is diluted by about 10 fold or less.
 32. The process ofclaim 3 wherein said concentrated protein solution is continuously mixedwith said chilled water to provide a dilution of the concentratedprotein solution by about 15 fold or less.
 33. The process of claim 32wherein said chilled water has a temperature of less than about 10° C.34. The process of claim 33 wherein said dilution is by about 10 fold orless.
 35. The process of claim 1 wherein the recovered protein micellarmass is dried to a proteinaceous powder.
 36. The process of claim 1wherein said recovered protein micellar mass has a protein content of atleast about 100 wt % (N×6.25).
 37. The process of claim 1 wherein saidoil seed meal is canola seed meal and, following recovering of theprotein micellar mass therefrom, the supernatant is processed, on abatch, semi-continuous or continuous basis, to recover additionalquantities of protein isolate therefrom.
 38. The process of claim 37wherein said additional quantities of protein isolate are recovered fromthe supernatant by concentrating the supernatant to a proteinconcentration of about 100 to about 400 g/L, preferably about 200 toabout 300 g/L, and drying the concentrated supernatant.
 39. The processof claim 37 wherein said additional quantities of protein isolate arerecovered from the supernatant by concentrating the supernatant to aprotein concentration of about 100 to about 400 g/L, preferably about200 to about 300 g/L, mixing the concentrated supernatant with therecovered protein micellar mass, and drying the mixture.
 40. The processof claim 37 wherein said additional quantities of protein isolate arerecovered from the supernatant by concentrating the supernatant to aprotein concentration of about 100 to about 400 g/L, preferably about200 to about 300 g/L, mixing a portion of said concentrated supernatantwith at least a portion of the recovered protein micellar mass, anddrying the resulting mixture.
 41. The process of claim 40 wherein theremainder of the concentrated supernatant is dried and any remainder ofthe recovered protein micellar mass is dried.
 42. The process of claim 1wherein, as an alternative to said diluting, settling and recoveringsteps, the concentrated protein solution is dialyzed to reduce the saltcontent thereof and to cause the formation of protein micelles, andrecovering a protein isolate from the dialyzed concentrated proteinsolution having a protein content of at least about 100 wt % (N×6.25) ona dry weight basis.
 43. The process of claim 42 wherein said proteinisolate recovery is effected by drying the dialyzed concentrated proteinsolution.
 44. The process of claim 1 wherein said oil seed meal iscanola oil seed meal.
 45. The process of claim 44 wherein the canola oilseed meal is cold pressed canola oil seed meal.
 46. The process of claim44 wherein the canola oil seed meal is derived from a non-geneticallymodified canola oil seed.
 47. The process of claim 1 wherein the oilseed meal is rapeseed meal.
 48. The process of claim 1 wherein said oilseed meal is mustard seed meal.
 49. The process of claim 1 wherein saidsolvent removal step is effected by air-desolventizing at a temperatureof about 15° to about 25° C.
 50. The process of claim 1 wherein saidsolvent removal step is effected under vacuum.